The utility model relates to an A.C. co-phase traction supply device of railway locomotive based on YN, vd wiring transformer; wherein, the traction transformer is a three-phase to two-phase balancing transformer (T), the wiring method of which is YN, vd. A rectifying inverter (Z) is connected between two outputs (b', c') of the line voltage of the transformer (T) and two outputs (a, x) of the phase voltage of the transformer (T), and the outputs (b', c') of the line voltage and the outputs (a, x) of the phase voltage are the supply ends (V1, V2) of the traction locomotive. Meanwhile, a control device of the rectifying inverter (Z) is connected with the two supply ends (V1, V2) of the traction locomotive. The utility model has the advantages of achieving the co-phase power supply in the whole line of the railway without dividing phases, being stable voltage in each section of the traction transforming station, ensuring that the locomotives can move at high speed when the locomotives are overloading, getting the power in three-phase from the public power network of the power supply system of the traction load of the railway, and eliminating the effect of the traction load of the railway to the power quality of the public power network can be eliminate, which can also be made by the prior traction transformer with low cost and convenient implementation.